[Bug c/71613] Useful warnings silenced when macros from system headers are used

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71613

--- Comment #4 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Candidate patch: https://gcc.gnu.org/ml/gcc-patches/2016-06/msg01658.html